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UNIVERSITY OF CALIFORNIA PUBLICATIONS 

IN 

AGRICULTURAL SCIENCES 

Vol. 2, No. 9, pp. 249-296, plates 45-52 December 31, 1924 



INHERITANCE IN 
CREPIS CAPILLAEIS (L.) WALLR. III. 

NINETEEN MORPHOLOGICAL AND THREE 
PHYSIOLOGICAL CHARACTERS 1 

BY 

J. L. COLLINS 



INTRODUCTION 

For several years variations in Crepis capillaris have been studied 
genetically. The study was commenced 2 in the hope of being able 
to determine whether the extensions of the Mendelian theory of 
heredity which were based on breeding data from Drosophila melano- 
g aster would hold for higher plants. For this purpose it was necessary 
to know the mode of inheritance of a number of characters. This 
paper is concerned with the description and mode of inheritance of 
a number of variations found in Crepis capillaris (L.) Wallr. 

It is evident that the material chosen for such a purpose should 
show variation of a hereditary nature and should also contain a low 
number of chromosomes. Crepis capillaris seemed to fulfil these 
requirements, for its chromosome number, 3 pairs, is the lowest 
reported for the higher plants, and the species is known as a variable 
one. 

Linkage has been demonstrated in a number of plants and in some 
of the higher animals. Unfortunately, the chromosome number in 
those species in which linkage has been observed is relatively high, 
and in no case is the number of groups of linked genes equal to the 
haploid number of the chromosomes. 



1 This is a report on a part of a project supported by appropriations from the 
Adams Fund. 

2 Studies commenced by Professor E. B. Babcock in 1915 and carried on by 
the writer under his direction since 1918; published as nos. 6 and 7 of vol. 2 in the 
present series. 



250 University of California Publications in Agricultural Sciences [Vol. 2 

Material and Methods 

The genus Crepis, containing over 150 species, is a member of the 
Cichorieae or chicory tribe of the Compositae, the best known related 
genera being Hieracium, Lactuca, Sonchus, and Taraxacum. 

Crepis capillaris (L.) Wallr. is an annual, but under certain cir- 
cumstances may assume the biennial habit. The plant first produces 
a rosette of radical leaves which have been found to vary in different 
plants from entire to bipinnately compound. The stem is usually 
single with paniculate branching above and varies from a few inches 
to four feet in height, largely depending upon conditions of growth. 
The cauline leaves are sessile, amplexicaul, clasping, the lower ones 
more or less lobed or pinnatifid, while the upper ones are slender and 
entire. The underside of the midribs of the rosette leaves, and to 
some extent the upper side, and the lower cauline leaves are more or 
less covered with bristly hairs. In many, but not all, plants the 
involucre and peduncle are glandular pubescent in addition to the 
fine gray tomentum which is always present. The brown terete 
achenes vary in length from 2 to 3 mm., are attenuate at both apex 
and base, and usually 10-ribbed. The yellow flower heads vary from 
17 to 25 mm. in diameter. 

During the course of the investigations, achenes of C. capUlaris 
have been obtained from many localities of the temperate and sub- 
tropical zones of both the old and the new world. The species is 
apparently a native of Europe, but is now disseminated throughout 
the world. 

The methods used in growing experimental cultures of Crepis 
have been previously published (Collins, 1922). 

In presenting data from hybrid populations, the degree of corre- 
spondence of observed with calculated distribution has been deter- 
mined by use of tables of probable errors of Mendelian ratios prepared 
by the Department of Plant Breeding of Cornell University. In the 
case of some dihybrid populations the method suggested by Harris 

( C )2 

(1912) has been used. This formula is X 2 = 2- , in which o 

c 

is the observed frequency of any class, c, the calculated frequency for 

( c )2 

that class, and 2 indicates that all the values of the type ■ are 

c 

added together. From Elderton's 3 tables for calculating the goodness 
of fit, the probability for the chance occurrence of the deviations in 
the observed classes has been obtained from the calculated value of X 2 . 



3 Given in Pearson, K., Tables for Statisticians and Biometricians, Cambridge 
Univ. Press, 1914. 



1924] 



Collins: Inheritance in Crepis capillaris (L.) Wallr. 



251 



VARIATIONS IN CREPIS CAPILLARIS 

Observations upon cultures grown from the achenes obtained from 
localities in many different regions have resulted in the discovery 
of a number of variations. Those which have been studied sufficiently 
to show their method of inheritance are described below. In assign- 
ing symbols to serve as genetic representatives of particular char- 
acters, the system in general use has been followed, namely, the use 
of the initial letter (or letters) of the name given to the character, 
small letters indicating a recessive, and capital letters a dominant 
condition. 

BALD (b) 

On August 17, 1918, a single plant (19.18P 23 ) in a culture of 47 
plants grown from achenes sent from Copenhagen was found to be 
devoid of glandular pubescence on the involucre and peduncle. This 
variation has been named ' bald. ' The second instance of this variation 
was in the same race but appeared only after two generations of 
inbreeding. Bald plants later appeared in cultures from other locali- 
ties as follows: Sweden, England, France, Chile, and the Azores. It 
was of importance to know whether the same or different genes were 
responsible for the appearance of 'bald' in cultures from such widely 
separated sources. This could be determined by crossing the different 
races. If a single gene were involved, then bald F x plants should 
result, while if, on the other hand, glandular plants resulted in the 
F x , this variation appearing in the different stocks would be the 
similar expression of different genes. As is shown in table 1, the 
same gene is present in each case. 

TABLE 1 

The Fi Results of Crossing Different Geographical Races of Bald 





Character of Fi 




Culture No. 


Bald 


Glandular 


Total 


F 2 Copenhagen X Sweden (20.130) X Chile (21.23).. 
Sweden (19.235) X Cambridge (19.66) 


9 
4 

56 
1 

7 







5 


9 
4 


Copenhagen (18.75) X Sweden (19.235) (19.H1, 
20.57-8, 21.101) 


56 


Chile (20.36) X Azores (20.40), (21.25). 


1 


Sweden (19.H3) X Azores (20.40), (21.117) 


12 







252 



University of California Publications in Agricultural Sciences [Vol. 2 



In the last item in table 1 both bald and glandular plants are 
recorded. This is as it should be, for the 19. H3 plant was an F x 
glandular plant produced by crossing the Swedish bald race (19.235) 
with a Eureka glandular race (19.224). If the bald gene in the 



TABLE 2 
F, Eesults from Crosses of BB X bb 





Character of Fi plants 


Pedigree No. 


Glandular (B) 


Bald (b) 


19.H3 

20.59 

21.21 

21.28 


2 
10 

7 
7 



1 
2 



Total 
Expected 1 : 


26 
29 


3 




TABLE 3 
Back Crosses of the F n Bb to bb 



Pedigree No. 


Progeny segregation 


B 


b 


21.17 

21.18 

21.19 

21.24 

21.117 

21.126 


7 
5 
6 
4 
12 
4 


3 
6 
7 
2 
13 
2 


Total 
Calculated 1 :1 


39 
38.5 


38 
38.5 


Deviation 


0.5 ± 3.84 



cultures from Sweden and from the Azores were identical, we should 
expect to obtain from such a back cross 50 per cent glandular and 
50 per cent bald plants. The 5 to 7 segregation obtained is a close 
approximation to the expected 1 to 1 ratio. While the Copenhagen 
race has not been crossed with the Cambridge race, nor the Chilean 



1924 



Collins: Inheritance in Crepis capillaris (L.) Wallr. 



253 



race with any except that from the Azores, we have evidence of their 
identity, since they have each been crossed with the Swedish race, 
which in turn was proved to be identical with the others. The bald 
plants from France have not been tested. Bald is inherited as a 
simple monohybrid recessive, as is shown by the results obtained from 
crossing with glandular plants. Table 2 presents F x data from crosses 
of bald X glandular. The one bald plant in culture 20.59 probably 
resulted from the failure to remove a single pollen grain during 
emasculation and represents an error in technique. The two bald 

TABLE 4 
F 2 Results prom the Cross BB X bb 





Progeny segregation 


Pedigree No. 


B 


b 


20.59 

20.60 

20.141 

20.142 

20.118 


10 

2 

56 

16 

74 


1 
3 

17 
7 

23 


Total 
Calculated 3:1 


158 
156.75 


51 
52.25 


Deviation 


1.25 db 4.22 



plants in culture 21.21 may be ascribed to this same cause or to errors 
at time of transplanting, since culture 21.23, containing only bald 
plants, grew adjacent to 21.21 in the flat before transplanting to the 
field. 

Table 3 shows that 39 glandular to 38 bald plants were obtained 
when the F x (bald X glandular) were backcrossed to the recessive 
parent strain. The expected 1 to 1 ratio was therefore realized. 

The results from F 2 cultures confirm the conclusion regarding a 
single recessive factor conditioning the appearance of bald. While 
in almost all cases involving bald the glandular hairs are completely 
absent, in culture 20.141 some plants appeared to be somewhat inter- 
mediate, inasmuch as they developed a few small scattered gland hairs 
on the involucre. They were easily distinguishable from glandular 
plants. In table 4 these intermediates have been classified as bald, 



254 University of California Publications in Agricultural Sciences [Vol. 2 

but in the original records they were designated as intermediates. 
If the culture 20.141, containing the intermediate-bald plants, is 
removed from the table, the remaining cultures give an exact ratio 
of 3 glandular to 1 bald; when the intermediates are classified as 
bald, the deviation from a 3 to 1 ratio is less than the probable error. 
The progeny of two bald and two glandular F 2 plants were grown. 
Both of the former gave, as expected, only bald offspring, while the 
two glandular F 2 plants produced both types in F 3 . 

The nature of the intermediate plants has not been definitely 
determined. The selfed progeny from one plant (18.dlP 76 ) gave a 
culture (20.55) of 18 bald, 3 intermediate, and 3 glandular plants. 
That they were not due to the incomplete dominance of the hybrid 
produced by crossing bald with glandular is certain, for in the F x 
cultures (table 2) all plants were fully glandular. Another inter- 
mediate bald plant (22.153P 18 ) produced 5 glandular and 5 bald 
plants from selfed seed but none that could be classified as inter- 
mediate. 

SMOOTH MIDEIBS (s) 

The midribs of the rosette leaves usually have a hairy pubescence. 
From sporadically appearing plants, races have been obtained which 
do not show these rib hairs; such plants have been designated as 
* smooth' (s). The F x resulting from a cross between these two types 
of plants were all rib-haired, and in the F 2 there appeared 556 rib- 
haired to 40 smooth plants. This is approximately a 15 to 1 ratio 
and suggests the operation of two independent genes, each producing 
the same somatic effect. 

Duplicate genes are by no means unknown, having been reported 
a number of times in the literature of genetics. If two independent 
genes were operating in the cultures 21.140 and 21.141, the F x of 
this same cross when backcrossed to smooth should give a 3S to Is 
ratio and some F 3 populations should give a 3 to 1 segregation. 
Evidence from cultures of these two types has been obtained; the 
data from them together with data from other crosses involving this 
character are given in table 5. The F 3 culture 21.189 was grown from 
one plant of an F 2 culture containing 58 rib-haired and no smooth 
plants. Such a deviation is, however, only three times the probable 
error and may well be due to errors of random sampling. The culture 
Fi 19. HI was originally made to determine the relation of the gene 
for bald of the English race of Crepis to that in the Danish race and 



1924 



Collins: Inheritance in Crcpis capillaris (L.) Wallr. 



255 



was the hybrid between these two races. The parent plant from the 
English race was smooth, while the parent from the Danish race had 
rib hairs. 

TABLE 5 
Showing F, and F 3 Results from the Cross SSS'S', SSs's', and SsS's' 

WITH SSS'S' 







Progeny segregal 


ion 


Pedigree No. 














S 






s 


F 2 21.140 




237 






17 


F 2 21.141 




319 






23 


F 3 22.189 


Total 


189 






9 




743 






49 


Cal( 


mlated 15:1 
Deviation 


742.5 






49.5 




0.5 ± 4.59 


F 2 22.55 




25 






12 


F 2 22.56 




5 






2 


F 2 22.60 




22 






6 


F 2 22.61 




4 






2 


F 2 22.62 




9 






1 


F 2 22.63 




34 






8 


F 2 22.41 


Total 


66 






24 




165 






55 


Ca 


Iculated 3:1 
Deviation 


165 






55 




0.0 ± 4.52 


Back 


cross 19. HI 


55 






17 


Ca 


Iculated 3:1 
Deviation 


54 






18 




1.0 db 3.83 



The 3 to 1 ratio obtained in 19. HI indicates that the rib-haired 2 
used was heterozygous for the duplicate genes for rib hairs. This 
cross, as regards these characters, was a back cross of a heterozygote 
to the recessive parent, and constitutes additional evidence to sub- 
stantiate the duplicate gene interpretation given above for the inherit- 
ance of rib hairs in these cultures. 



256 University of California Publications in Agricultural Sciences [Vol. 2 



LEAF VARIATIONS 

From the very first acquaintance with C. capillaris, the different 
forms in the rosette leaves constituted the most striking and out- 
standing variations. They have proved equally as difficult to study 
genetically, due, first, to the difficulty in evaluating non-genetic 
variability resulting from age of plant and from environmental causes, 
and, second, to the complex heterozygotic nature of the material in 
the wild condition. Sears (1921) found in T araxacum that the degree 
of leaf dissection is correlated with the age of a given rosette. The 
leaves of a very young rosette are almost entire, becoming progres- 
sively more dissected as the rosette becomes older. Stork (1920), 
also working with Taraxacum, found that in very young plants 
the rosette leaves ranged in form from entire to deeply pinnatifid- 
runcinate, but became more, instead of less uniform, as they grew 
older. Neither condition can therefore be taken as typical for that 
species. In Crepis, a closely related genus, there is a more regular 
sequence of development of leaf shape for a particular rosette. The 
juvenile leaves are usually entire or nearly so, and assume their 
typical forms gradually as the plant reaches the mature rosette stage 
just preceding the appearance of the flowering stalk. At this time 
there exist individual differences which range in form from entire 
to deeply pinnatifid or compound pinnatifid. That these differences 
are genetic is shown, first, by the fact that inbreeding has resulted 
in the isolation of races of the different types which breed true when 
grown side by side under similar conditions, thus to a large degree 
eliminating the effect of the non-genetic factors, and, second, that 
the forms when crossed give a fairly uniform F x and segregate into 
the parental and F x forms in the second generation. 

By means of inbreeding and selection, a number of distinctive, 
uniform races have been obtained in almost homozygous condition. 
A brief description of each is given below. 

VIEIDIS 
Plate 45, figure 1 

This form was isolated in 1919 from the Eureka (California) 
stock. The rosettes are small, 4 to 10 inches in diameter. The leaves 
are deeply lobed or pinnately parted, and are lacking in anthocyanin. 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 257 

The blade of the leaf is of a darker color than the midrib. The color 
of the blade is Ridgway's varleys green, 31' m. The midrib is covered 
on both upper and lower surfaces with hairy pubescence. The lobes 
are usually widest at the base, often having a minor lobe attached to 
the proximal edge of the base of the major lobe. Attached to the 
midrib between the lobes is a narrow wing. The lobes are usually 
close together, with the terminal lobe slender and pointed. 

H6 RACE 
Plate 45, figure 2 

The H6 race was isolated in 1919 from a Berkeley Crepis stock. 
The size of the rosettes is more variable than in viridis, the rosettes 
ranging from 8 to 12 inches in diameter. The leaves are pinnately 
and bipinnately lobed ; the lobes are constricted at the base and 
rounded at the tip, and inclined to twist, so that the plane of the lobe is 
not in the same plane with the midrib. Anthocyanin is conspicuously 
present. There are no hairs on the midrib. The lobes, usually six 
in number, are widely spaced. The terminal lobe is large and blunt- 
tipped. The narrow wing on the midrib is crimped, presenting a 
ruffled effect. The wing and edges of the lobes contain a blackish 
purple coloring which appears very early in the development of the 
plant. The leaf color, according to Ridgway's Standard, is cedar 
green, 31m. The characters which make up this type are dominant, 
excepting smooth ribs, when crossed with viridis. 

PALLID 
Plate 45, figure 1 

This race was obtained in 1919 by inbreeding in the same Eureka 
stock that produced the viridis race. The rosettes are from 6 to 10 
inches in diameter. This race produces more leaves in the rosette 
than do the preceding races, giving the rosette a thick mat-like appear- 
ance. Pallid lacks anthocyanin and is a much paler green (Ridgway's 
forest green, 29'm.) than the two races described above. The lobes 
are broadest at the base, are set closely together, and have pronounced, 
pointed teeth. This race does not grow so rapidly as the darker green 
races. Rib hairs are present on the midrib. 



258 University of California Publications in Agricultural Sciences [Vol. 2 

SIMPLEX Z9 
Plate 46, figure 1 

Simplex Z9 was isolated in 1920 from a stock originating from 
seed collected at Quy Fen, England. The original culture consisted 
of plants ranging from entire to pinnatifid. The simplex Z9 race was 
obtained by inbreeding plants with entire leaves. Although inbreed- 
ing has reduced the amount of variation, there still appears in this 
supposedly homozygous race a small percentage of semi-pinnatifid- 
leaved plants (pi. 46, fig. 1). Anthocyanin and rib hairs are present. 

SCALAEIS e29 
Plate 46, figure 2 

This race was isolated in 1919 from the Eureka stock of Crepis 
which produced the viridis and the pallid races. It is characterized 
chiefly by long, simple, pinnately-divided leaves with pointed lobes. 
The terminal lobe is slender and elongated, often curved to one side 
near the tip. Both anthocyanin and rib hairs are present. The 
average number of lobes per leaf is 10. It is clominent when crossed 
with simplex Z9 or with viridis. Typical leaves of the scalaris e29 
and the simplex Z9 races are shown in plate 52, together with the 
F x and F 2 types obtained when these two races are crossed. In the 
F 1 a few extreme variants occur which approach the simplex form, 
but the majority are more nearly like the scalaris and constitute a 
fairly uniform intermediate type. In the F 2 , three types are dis- 
tinguishable (see pi. 51, fig. 2), the two grandparental forms and an 
intermediate scalaris form similar to the F 1 . When the intermediate- 
scalaris and the scalaris are grouped together a 3 to 1 ratio is obtained 
(see table 6).. The intermediate forms differ from the scalaris in 
having the lobes less deeply incised, some more so than others, but 
still classifiable as intermediate. (See third and fourth leaves in 
P 2 , pi. 52.) 

From the results of breeding it appears that there is present one 
main gene for lobing and that dominant modifying genes are involved 
which act cumulatively, thus producing intermediates of different 
grades of pinnate lobing. As a corollary to this hypothesis races 
breeding true for different grades of intermediate pinnatifid lobing 
should be possible. There is evidence that such races occur. Several 
intermediate forms have been tested and found to be fairly constant. 



1924 j Collins: Inheritance in Crcpis capillaris (L.) Wallr. 259 

A race obtained from Seattle, Washington (named "Seattle") 
appears to be such a homozygous intermediate form. 

Races of Crcpis capillaris also differ in number of lobes per leaf 
and in length of leaf (Rau, 1923). The scalaris race shown in plate 
52 has a large number of lobes. The two races differ, however, in 
length of leaf. The leaves of the scalaris parent shown in plate 52 
are shorter, and of the simplex parent larger, than the mean size 
typical for each race. The F x is usually larger than either parent. 
The F 2 in the same figure shows the segregation for size which appears 
to be due to multiple genes. 

The inheritance of pinnatifid and entire leaf forms in capillaris 
conforms in general to the type of inheritance of corresponding forms 
in a number of other plants. Rasmusen (1916) found in species 
crosses in grapes that differences in leaf form behaved in a very 
similar way. The F 1 appeared to be intermediate between the shapes 
of the parent leaves. In the F 2 , a series was produced which included 
the grandparental forms, the F x type and different grades of inter- 
mediates. If the deeply toothed and intermediate toothed classes were 
grouped together, a ratio of 3 toothed to 1 non-toothed resulted. 

Shull (1918) found four different leaf forms of the shepherd's 
purse to be caused by two pairs of factors. As in Crcpis, the deeply 
pinnatifid forms were dominant. The plants were also subject to 
considerable fluctuating variation. Two races of Urtica, one having 
deeply serrated leaves, the other, leaves with entire edges, gave 
serrated leaves in F x and a ratio of 3 serrated to 1 entire leaf in 
the F 2 generation (Correns, 1912). In cotton, however, the deeply 
palmately parted leaf form is not dominant when crossed with the 
five-pointed upland type, but produces an intermediate type in F t 
with a ratio of 1:2:1 in the F 2 generation (Shoemaker, 1909). 
Kristofferson (1923) found that the difference in lobing of the leaves 
of two species of Malva was brought about through a single genetic 
factor, and resulted in a somewhat intermediate condition in F x and 
a 3 lobed to 1 non-lobed condition in the F 2 , although considerable 
variation in the degree of lobing in the pinnatifid class was recognized. 
Tedin (1923), on the other hand, found that pinnatifid and entire 
leaved plants differed genetically by two factors. 



260 



University of California Publications in Agricultural Sciences [Vol. 2 



TABLE 6 
The Eesults from the Cross of Leaf Forms. Sc X sc 





Progeny segregation 


Pedigree No. 


Sc 


sc 


21.140 

22.7 

22.10 

22.14 

22.17 

22.19 

22.22 

22.24 

22.25 . 

22.26 


177 
99 
50 
14 
48 
92 

167 
51 
37 
29 


75 
24 
17 

6 
15 
19 
52 
14 
13 

2 


Total 
Calculated 3:1 


764 
750.75 


237 
250.25 


Deviation 


13.25 ± 9.24 



SCALARIS e28 (Sc) 
Plate 47, figure 1 

This pinnatifid leaf form was isolated in 1919 ; it originated from 
a single plant which was a sib to the one producing the scalar is e29 
race. These two forms have much in common, but are different in 
size, e28 being smaller and not so vigorous as e29, and having shorter 
and blunter lobes. 

Two races of the pinnatifid leaf forms isolated from the Berkeley 
(H6) race of plants and from the Eureka population (e28), respec- 
tively, differ in a number of minor characters, as shown in the follow- 
ing comparative list : 



H6 (Berkeley) 
dark green 
dark green to blackish 
pronounced 
pronounced 
none 

pronounced 
blunt and rounded 
rounded 
wide (very) 
pronounced 
large 



Characters 
color of leaf 
color of midrib 
anthocyanin 
crimping of rib-wing 
rib hairs 

black edge on leaf 
terminal lobe 
lateral lobe 
lobe spacing 
Constricted base of lobes 
secondary lobes 



e28 (Eureka) 
dark green 
light green 
none or trace 
none 
present 
trace only 
narrow — pointed 
slender — more pointed 
wide (medium) 
none or trace 
none 



1924] 



Collins: Inheritance in Crepis capillaris (L.) Wallr. 



261 



Plants of these two races when crossed showed almost the entire group 
of H6 characters (rib hairs excepted) in the ¥ 1 , while in P 2 (21.141) 
there appeared the parental types and in addition some composite 
types that showed some characters from each parent. When each 
character pair was considered separately, however, a peculiar sit- 
uation was presented. Six of the character pairs gave 9 to 7 ratios, 
and a seventh pair, rib hairs vs. smooth ribs, gave a 15 to 1 ratio. 
The data for these characters are included in table 7. It is quite 
probable that these six character pairs as given are the result of not 
more than three sets of genes, since the two characters, black edging 
of the leaves and anthocyanin of the midribs, are both concerned with 
the distribution of anthocyanin pigment in the plant. The shape of 
the terminal and of the lateral lobes is probably conditioned by the 
same pairs of genes, while the crimping of the wing of the midrib 
and the constriction of the base of the lobes also probably result from 
the action of the same gene. The Berkeley plants were evidently 
homozygous for the dominant complementary genes of all three 
character couples. This genotype may be expressed as AA'BB'CC, 
the simultaneous presence of both the primed and unprimed dominant 
genes being necessary to cause the development of the respective 
characters. The Eureka race would then have the genotype aa'bb'cc' 
with respect to these characters. 

TABLE 7 

Segregation of Six Pairs of Characters in the F 2 from the Cross 
H6 X Scalaris e28. (Culture 21.141) 



Segregation 


Calculated 
9 :7 


Deviation 


162 black edge : 103 green edge 


149.06 : 115.93 
154.71 : 120.33 

143.1 : 111.3 
143.1 : 111.3 

143.1 : 111.3 
149.58 : 116.34 


12.94 ± 5.45 


166 anthocyanin : 109 none 


11.29 ± 5.55 


142 angular lobes : 112 round 


1.1 ± 5.33 


150 narrow lobes : 104 broad lobes 


6.9 ± 5.33 


135 constricted lobes : 118 non-constricted 

165 crimped wing : 101 flat wing 


8.1 ± 5.32 
15.42 ± 5.49 







BEVOLUTE (r) 

Plate 47, figure 2 
This race appeared in 1919 among offspring of a plant of the 
Eureka stock, which had been self -pollinated. The plants are char- 
acterized by a definite downward curling of the edge of the leaf 



262 



University of California Publications in Agricultural Sciences [Vol. 2 



toward the midrib. It occurs in both entire and pinnatifid types, 
though it is more conspicuous in the former. In appearance much 
like the fwmfolia mutant of Oenothera Lamarckiana described by 
Shull (1921), in which both rosette and cauline leaves have edges 
curled under. The knowledge of the genetic basis for this character 
has been obtained incidentally in experiments designed to show in- 
heritance of other characters. The data thus obtained indicate that 
revoluteness is conditioned by complementary recessive genes. 



TABLE 8 
Showing the Segregation of Eevolute Leaves in Two Cultures 





Progeny segregation 


Pedigree No. 


R 


r 


19.e5 
Calculated 3:1 


62 
59.25 


17 
19.75 


Deviation 


2.75 ± 2.60 


21.140 
Calculated 15:1 


233 
237.19 


20 
15.81 


Deviation 


4.19 ±2.60 



It is significant that revolute appeared only in these two cultures, 
which were derived from a common source, because it indicates that 
the genes were present in the wild plants from which the starting point 
of these cultures was obtained. The 15 to 1 ratio made its appearance 
in the sixth generation from the wild plants (some out-crossing occurs 
in this pedigree), while the 3 to 1 ratio appeared in the second gen- 
eration. 

BICEPHALIC (bi) 
Plate 48, figure 1 
This character designates a type of fasciation in which the buds 
are more or less joined together in twos. The peduncle is also fre- 
quently flattened. This variation was first found in 1920 on a single 
plant (20.30) which was grown from achenes obtained from Chile. 
This original plant was crossed with 20.130P 19 , which produced an 
F x culture of 9 normal plants. The F 2 , consisting of 81 plants, segre- 
gated into 60 normal to 21 bicephalic, clearly a monofactorial ratio. 



1924J 



Collins: Inheritance in Crepis capillaris (L.) Wallr. 



263 



In no case were all the buds of a plant of the bicephalic kind. Some 
plants indeed produced only a few double buds. F 2 bicephalic plants 
of both types were selfed and F 3 cultures produced. The data from 



F 3 cultures are shown in table 9. 



TABLE 9 

Type of Plants Produced by Selfing F 2 Bicephalic Plants 



F 2 Plant No. 


Progeny F 3 


23.283 








Bicephalic 


Normal 


*P 6 8 + 


6 


1 


P70 + 


2 


6 


P 9 6 + 


8 





P« + + 


6 





P 10 + + 


6 





P 2 3 + + 


5 


1 


P24+ + 


2 





P30+ + 





1 


P44+ + 


20 





P46+ + 


8 





P48+ + 


5 


2 


P57+ + 


2 





P 8l + + 


5 


(2?) 



* The single + indicates an F 2 plant on which but few bicephalic buds appeared. 
The ++ indicates plants having many such buds. 

It appears that F 2 bicephalic plants breed true in F 3 . Plant 70 
which had only a few double buds, was apparently a heterozygote, for 
it gave a 3 to 1 ratio in F 3 . The other F 3 plants listed as normal 
may have been genetically bicephalic, since they showed some evi- 
dences of f asciation in the stems and malformation of buds ; but no 
doubling or cohesion of the buds was found. 



ANTHOCYANIN 

This pigment is distributed to many parts of the plant, but is 
most noticeable in the midribs of the leaves and on the lower portions 
of the stems. Culture 19.e8 segregated into 94 plants with antho- 
cyanin to 39 with none or developed only to a slight degree. The ratio 
in this case is 2.82 to 1.17, in which the deviation is less than twice 
the probable error. This segregation can be considered only as sug- 
gestive because of the difficulty of accurately classifying this character 



264 University of California Publications in Agricultural Sciences [Vol. 2 

in Crepis. The appearance of purple anthocyanin color depends upon 
a certain amount of sunshine and exposure to light. Plants known 
to be capable of producing the color will show it to only a small degree 
if conditions for anthocyanin development are adverse, while, on the 
other hand, races in which it does not normally appear conspicuously 
will produce it under conditions of sudden exposure to direct sun- 
shine or sometimes as a result of mutilation caused by animals or 
insects. The development of anthocyanin is a matter of degree, for 
the potentiality for its development is not entirely absent from any 
race so far obtained. In the viridis race we have it in its lowest and 
in the H6 race in its highest development. Crosses between high and 
low anthocyanin races (other than 19. e8 mentioned above) in general 
produced F x plants showing the darker anthocyanin of the H6 race, 
but in F 2 produced a series of forms showing a gradation in pigment 
from one parent to the other. In most cases the parental types were 
also duplicated. One such cross, H6 X viridis e33, gave an F 1 more 
nearly like the H6, but in F 2 the types were distributed as follows: 
9 of H6, 3 of viridis, and 3 distinctly between these two parental types. 
The segregation of anthO'Cyanin has been observed in other cultures 
(e26= 3 to 1), but has not, in general, given sufficiently regular 
results to warrant the drawing of conclusions regarding its genetic 
basis. The analysis can only proceed when facilities are available to 
control more accurately the environmental factors which alter its 
development. 

DWAEF II (dll) 
Plate 48, figure 2 

This variation first appeared in culture 21.99, which was the 
second selfed generation from achenes obtained from Lyons, France. 
It is characterized by a very small rosette of slender semi-scalaris 
leaves which are blotched with yellow and yellowish red coloration, 
giving them the appearance of being about half -dead. Due to their 
peculiar appearance the first plants were thought to be suffering from 
poor environment, although adjacent plants were healthy. The plants 
when mature are very small (3-6 inches in height), the stems very 
fine and spreading. In the first culture the dwarf effect appeared to 
be recessive (5 dwarfs in 16 plants) and bred true in the next gene- 
ration. Culture 22.159 from 21.99P 7S , a normal plant, contained 51 
plants, 3 of which were dwarf II and 3 somewhat dwarfish but not 
typical for dwarf II. This is approximately a 15 to 1 ratio, and 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 265 

indicates that there may be duplicate genes for dwarf II ; sufficient 
data are not at hand to establish the hypothesis. Culture 22.160 
(from 21.99P ir „ a normal plant) gave 84 normal plants. 

The yellow appearance of the leaves in dwarf II seems to be a 
dominant character from its appearance in 22.407, F x of the cross 
22.169P 22 X 22.261P 4 , the male parent being a dwarf II plant from 
a pure culture. Inasmuch as the F x plants are not dwarfish, it appears 
that the yellowing and dwarfing may be due to separate but probably 
linked genes. All the dwarf II plants which have appeared were 
yellowish, and we may therefore assume that, instead of linkage, 
the appearance of dwarf II is dependent on the presence in the zygote 
of the dominant gene causing yellowing. 

DWARF III (dill) 
Plate 49, figure 1 

This variation first appeared in 1919 culture e5. It reappeared in 
1921 in a culture (21.76) which came from the same source as e5. 
The ratio of normal to dwarf III in 21.76 was 15 to 1, and in the 
progeny of 21.76?! (culture 22.117) 3 to 1. (See table 10 for data.) 
Dwarf III was at first called 'semi-lethal, ' because of the high mortality 
in this class of plants. These plants remain very much smaller than 
their normal sibs during the rosette stage and reach maturity much 
later. A large percentage die after they have formed a rosette and 
before they reach the flowering stage. 

This variation appeared in several members of the same stock 
which produced revolute, viridis, and pallid. 

SPREADING (sp) 
Plate 49, figure 2 

A lax, open-branching habit which appeared in 20.37, the French 
stock of Crepis. The stems and branches are long and slender, appear- 
ing to be so weak they cannot support themselves in upright position. 
Dwarf II appeared in this race and all have this spreading habit. 
Data from crosses (21.26 and 22.173, table 10) show that it is a reces- 
sive character. When the same plant (20.37P 3 ) was crossed to another 
erect plant (19.in.Pu), it behaved as a dominant (21.28, 22.41, and 
22.43, table 10). Of the F 2 cultures, only 22.173 was grown under 
desirable conditions; the others were overcrowded in greenhouse and 
lath house, which interfered with proper development of this char- 
acter. 



266 



University of California Publications in Agricultural Sciences [Vol. 2 



PROCUMBENT (p) 

This variation is similar in appearance to spreading. It first 
appeared in culture 20.40, which came from achenes sent from the 
Azores Islands. Unlike spreading, it seems to be dominant, the F x 
plants, 21.28 (from 20.40P X 20.111PJ, being of the procumbent 
type. The F 2 cultures were grown under crowded and unfavorable 

TABLE 10 
Segregation of Plant Characters 





Segregation 


Culture No. 


Normal 


Variant 


21.76 
Calculated 15:1 


57 
57.19 


4 dwarf III 
3.81 


Deviation 


0.19 db 1.28 


22.159 
Calculated 15:1 


48 
47.81 


3 dwarf II 
3.19 


Deviation 


0.19 ± 1.17 


22.117 
Calculated 3:1 


12 
12 


4 dwarf III 
4 


Deviation 


0.0 ± 1.17 


22.99 
Calculated 3:1 


11 
12 


5 dwarf II 
4 


Deviation 


1.0 ± 1.17 


22.173 
Calculated 3:1 


70 erect 
72 erect 


26 spreading 
24 spreading 


Deviation 


2.0 ± 2.86 


22.41 
22.43 

Total 
Calculated 1 :3 


18 
5 

23 
19.2 


39 spreading 
15 spreading 

54 

57.8 


Deviation 


3.8 ± 2.56 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 267 

conditions which made accurate classification difficult and uncertain. 
One F 2 gave a 1 to 1 ratio and another the ratio 2 procumbent to 1 
normal. 

ERECT (e) 
Plate 50, figure 1 

A strain characterized by erect habit of growth, large stiff lateral 
branches, and a thick rigid central axis. The branches make an acute 
angle with the axis, the whole plant having the form of an inverted 
cone. This form was selected from the F 2 of a cross between the 
Danish and Swedish stocks. 

PALE A (p) 
Plate 51, figure 1 

The nature of this character has previously been discussed (Collins, 
1921). It originally appeared in an F x hybrid and was considered a 
reversion to a possible, pre-composite, ancestral condition. It has 
appeared in every case in hybrids, never in inbred races, and was 
probably introduced with the Danish stock, since the same plant 
(17.198P 2 ) of that stock is in the pedigree of all the hybrids which 
have produced palea. Races homozygous for palea have been 
obtained. Preliminary data show palea to be conditioned by a single 
recessive gene. 

Linkage 

In a species having only three pairs of chromosomes, it would 
seem fairly easy to establish groups of linked genes, especially when 
the species was known to be more or less polymorphic. However, it 
has not yet been possible to realize this end, due to the unexpected 
relations of some of the genes in this species. For instance, there 
are four cases of complementary recessive genes, and three characters 
dependent upon duplicate dominant genes. The determination of 
linkage groups under such conditions is complicated because it re- 
quires a longer time to obtain races with a known and tested genotype. 

The gene for bald involucre appears from data in tables 12 and 13 
not to be linked with the gene for smooth ribs nor with the gene for 
procumbent, since the ratios show independent segregation. 

It is of course obvious that linkage must occur between one pair 
of complementary genes for smooth ribs and one pair of complemen- 
tary genes for revolute leaves, since there are four pairs of genes and 



268 



University of California Publications in Agricultural Sciences [Vol. 2 



only three pairs of chromosomes. A cross involving these two char- 
acters gave the following results (+ indicates the presence and — the 
absence of the character named) : 

TABLE 11 

Dihybrid Segregation of Smooth X Revolute in a Culture which Gave a 
15: 1 Ratio for Each Character Separately 



Culture 
21.140 


Smooth ribs 
Revolute leaves 


: 


+ 


+ 


+ 
+ 


Total 




Observed 
Calculated 
57 : 3 : 3 : 1 : 


202 
224 


16 
11.79 


32 
11.79 


2 
3.93 


252 
252 




(o-c) 2 
c 


1.98 


1.50 


34.64 


0.12 


X 2 = 38.24 
P =.0000 



The calculated numbers agree fairly well with those obtained 
except in the third class where the observed numbers are more than 
twice as large as the calculated number. This class may have been 
increased at the expense of the first class by placing in it some plants 
which genetically belonged in the latter. The observed number in 
the first class is considerably less than the calculated number for that 
class. These figures indicate that the genes are arranged in the three 
pairs of chromosomes as follows: R, s, — (R'S') (rV) — r, S, where 
primed genes are the complements of the unprimed genes. Were the 
linkages as follows (R's) and (r'S), the F 2 population should consist 
of three classes in the proportion of 14 :1 :1, assuming that little or 
no crossing over occurs. A high percentage of crossing over in the 
latter type of linkage would give approximately the results obtained. 
It appears, therefore, that either the dominants are linked, as stated 
above, or that there is a high percentage of crossing over between the 
linked genes. This inference can be tested experimentally, for races 
have been obtained which gave 3 to 1 ratios for both of the characters. 



Effects of Inbreeding 

The flowers of Crepis are perfect and, although self-fertilization 
can take place, the arrangement of the stigmas in respect to the 
stamens is such as to permit cross-pollination before self-pollination 
can be naturally effected. The stamens are united into a tube sur- 
rounding the style, and the pollen is shed on the inside of this tube. 



1924] 



Collins: Inheritance in Crcpis capillaris (L.) Wallr. 



269 



TABLE 12 

F 2 Eesults from the Dihybrid Cross, Glandular and Hairy Midrib X Bald 
and Smooth Kibs, Showing Independent Segregation 



Culture 
22.41* 


Observed 
segregation 


Calculated 
segregation 
9:3:3:1 


(o-c) 2 
c 


Glandular 








and 


36 


41.01 


0.61 


Rib Hairs 








Glandular 








and 


11 


13.68 


0.52 


Smooth 








Bald 








and 


20 


13.68 


2.84 


Rib Hairs 








Bald 








and 


6 


4.56 


0.42 


Smooth 










73 


72.96 


X 2 = 4.39 
P =0.2264 



*Rib hairs vs. smooth in this culture show a 3 : 1 ratio. 



TABLE 13 

Showing Independent Segregation in F 2 of Dihybrid Cross, 
Glandular-Erect X Bald-Procumbent 



Culture No. 
22.41 


Observed 
segregation 


Calculated 
segregation 
9:3:3:1 


(o-c) 2 
c 


Glandular — 
procumbent 


17 


20.25 


0.37 


Glandular — 
erect 


10 


6.75 


1.56 


Bald- 
procumbent 


7 


6.75 


0.01 


Bald- 
erect 


2 


2.25 


0.03 




36 


36.00 


X 2 = 1.97 
P = .5773 



270 University of California Publications in Agricultural Sciences [Vol. 2 

The style is bifid with the stigmatic surface on the adjacent faces 
of the lobes. With the beginning of anthesis the style elongates, 
pushing the upper end out from the stamen tube and sweeping the 
pollen out with it on its outer surface. The stigmatic lobes then 
separate and assume a position at right angles to the style. The pollen 
at this stage is below the receptive surface of the stigma, which is, 
however, exposed to insects, the means by which cross-pollination is 
effected. Later the stigma lobes curl into a short spiral which brings 
the receptive surface of the stigma in contact with its own pollen or 
that of an adjacent floret of the same head. Under natural conditions 
Crepis is often cross-pollinated by insects, and this preserves a 
heterozygosity of the germinal material. A similarity of the effects 
of continued inbreeding in Crepis to the effects of inbreeding in maize 
has been noted (Collins, 1920). It was shown that inbreeding caused 
a reduction in the size of the plants and increased the length of the 
vegetative period. Other data are now available which show in 
another way the general heterozygosity of Crepis capillaris as it 
occurs in a wild state. Thus the seed collected from a few wild plants 
near Eureka, California, has been the source of the following races: 
viridis, scalaris-e28, pallid, and revolute (leaf form variations) ; of 
three types of partial albinos (chlorophyll development) ; and of the 
variations, dwarf III and fasciation (the plant as a whole). From 
the Berkeley wild plants we have obtained plants with smooth ribs 
and the leaf form H6 ; from England, the leaf form simplex-Z9 ; from 
France, dwarf II, spreading, chlorina, and tubular flowers. Palea 
probably came from the Danish material. As mentioned in another 
section, bald has appeared independently in the cultures from six 
different geographical regions. The Eureka stock has produced the 
greater number of new races. This is not taken to mean that it is 
necessarily more heterozygous but that many more plants from this 
source have been under observation. We have presented here an 
instance of a remarkable germinal diversity in locally developed 
strains of a single species. Although many of the characters appeared 
only after hybridization between local races or stocks, the evidence 
does not, except in a few cases, show these characters to be due to 
complementary factors. The appearance of bald from such widely 
separated localities as Chile and Sweden and from other less widely 
separated localities is of particular interest, for it shows that either a 
certain locus of the germinal material mutates more readily than 
others or that all these local races have originated from a single stock 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 271 

in which this gene was present ; the former is, however, more probable, 
for it has been shown in Drosophila (Sturtevant, 1921) that certain 
loci are more mutable than others. Additional evidence that this is 
the case is found in the fact that a similar variation, bald, has been 
found to occur in at least four other species, C. bursifolia, C. biennis, 
C. aspera, and C. dioscoridis. A similar germinal diversity among 
local races of Drosophila m-elanog aster from equally widely separated 
localities has not been found, and Sturtevant suggests that this may 
be due to a frequent transportation of individuals from one locality 
to another. The chances are probably as great for transportation of 
Crepis seeds along with agricultural seeds as for the transportation 
of Drosophila among fruits. 

It is possible that some of these variations might have arisen from 
mutations occurring in the cultures under observation. A study of 
the wild plants in the fields about Eureka, however, disclosed the 
fact that some of the forms obtained in the greenhouse by inbreeding 
were also appearing there among wild plants. In this material it is 
impossible to say whether any new recessive variation appeared as the 
result of a recent gene mutation or the segregation of a recessive from 
a heterozygous parent stock. 

Variations in Chlorophyll 

A number of different variations involving a loss of chlorophyll 
have appeared. These variations are evident in the seedling stage, 
but, unlike the usual albinic condition in seedling plants, most of these 
albino types develop sufficient chlorophyll as the plant grows to enable 
the plant to live. One type of pure white seedling always dies in the 
seedling stage. The other types are either pure yellow or yellowish 
green. The percentage of seedling mortality in these classes is higher 
than in pure green seedlings. 

A complete analysis of the genetic relations of these different types 
has not yet been possible, but a sufficient study has been made to 
warrant a preliminary report in this general account of variations in 
Crepis capillaris. 

CHLOEINA (C) 

Chlorina signifies a chlorophyll deficiency in seedling and mature 
plants. The middle portion of the leaves of chlorina plants is yellow- 
ish, but both tip and base contain more or less chlorophyll and thus 
it is possible for the plant to function. This character first appeared 



272 



University of California Publications in Agricultural Sciences [Vol. 2 



in culture 21.99. In 1922 a culture of six chlorina plants was obtained. 
When these chlorina plants were crossed with normal green plants, 
the two classes of plants — normal and chlorina — appeared in the 
progeny in equal numbers, thus indicating that the chlorina plants 
were heterozygous for green. Self-fertilization of the green resulted 
in only green progeny. The seedling progeny from self-fertilized 
chlorina plants consisted of three classes : pure yellow, pale green, and 
normal green, in the ratio 1 to 2 to 1. The yellow seedlings died, the 
pale green ones developed into chlorina plants, and the green seed- 
lings produced only green plants. The gene for chlorina is therefore 
dominant and has a lethal action when homozygous. 

TABLE 14 

Segregation of Seedling Progeny of Self-fertilized Chlorina Plants 



Culture No. 


Green 


Pale green 


Yellow 


24.171 
24.173 
24 . 174 


46 
13 
66 


60 

17 

? 


26 

6 

33 


Total 


125 


77 


65 


Observed 
Calculated 3:1 


202 
200.25 


65 
66.75 


Deviation 


1.25 ±4. 77 





In table 14 the seedlings in culture 24.174 intergraded in such a 
way that it was impossible to make an accurate segregation of pale 
green from green; consequently the two classes are combined in the 
table. Separation of the two green types in other cultures was less 
difficult, although it is apparent that some pale green plants have been 
included in the green class. 



GOLDEN YELLOW (y) 

The type known as golden yellow behaves as a monohybrid reces- 
sive as shown by data in table 15. 

These golden yellow seedlings gradually develop chlorophyll and 
finally reach maturity, although growing much more slowly than 
their green sibs. These plants can, however, be distinguished in the 
mature stage, due both to size and to the peculiar distribution of the 
chlorophyll. They produce mature rosettes that show a mottling 



1924 



Collins: Inheritance in Crepis capillaris (L.) Wallr. 



273 



of yellow and green through the leaves, which looks much like the 

plant disease known as ' mosaic, ' or rosettes on which the central and 

thus younger leaves of the plant are a clear yellow. These yellow 

leaves later develop chlorophyll and become normally green. 

It would appear from table 15 that the golden yellows would be 

homozygous recessives ; but this is not the case, for the seedlings from 

selfed 'yellow center' and from 'mottled' plants show some of them 

to be heterozygotes. Only one plant has yet been found which was 

homozygous for yellow. 

TABLE 15 

monohybrid segregation of golden yellow in the progeny of 
Green Plants 



Culture No. 


Progeny segregation of seedlings 


1921 








Green 


Yellow 


177P 13 


10 


3 


177P 16 


12 


3 


177P 17 


278 


84 


177P 38 


13 


5 


177P 40 


15 


3 


177P 78 


36 


10 


177P 124 


23 


6 


Total 


387 


114 


Calculated 3:1 


375.75 


125.25 


Deviation 


11.25 ± 6.54 



That there are other genes which also produce yellow seedlings is 
evident from table 16. The three plants P 39 , 66 , and 76 were green 
as seedlings and normal green in the mature stage. They apparently 
were heterozygous for two recessive genes which produced the same 
or a very similar type of yellow. The progeny of P 25 indicate still 
another type of yellow indistinguishable phenotypically from those 
already mentioned. Here the production of chlorophyll in the seed- 
ling stage is dependent on the simultaneous presence of two dominant 
genes, and the absence of either one results in a yellow type of 
seedling. 

Trow (1916) reports a similar case of complementary recessive 
genes in the production of albino seedlings in Senecio, another genus 
of the Compositae. 



274 



University of California Publications in Agricultural Sciences [Vol. 2 



TABLE 16 

Showing Seedling Segregation in the Progeny of Green Plants Indicating 

Complementary Eecessive Genes for Golden Yellow and 

Duplicate Genes for Chlorophyll 





Progeny segregation of seedlings 


Culture No. 


Green 


Yellow 


21.177P 39 
21.177P 66 
22.177P 76 


44 
13 
45 


3 
1 
3 


Total 


102 


7 


Calculated 15:1 


102.19 


6.81 


Deviation 


0.19 ± 1.70 


21.177P 25 

Calculated 9:7 


22 
19.687 


13 
15.312 


Deviation 


2.312 ± 1.98 



VIEESCENT YELLOW (v) 

A third type of seedling called virescent yellow has a small amount 
of green color in addition to the yellow. These seedlings, like the 
yellow ones, may produce two types of mature plants, namely, pure 
green plants and green plants with pale green younger leaves at the 
center of the rosette. The data at present indicate that virescent 
plants are produced when a gene dominant to yellow but recessive to 
green is present with the gene for yellow, which changes yellow seed- 
lings to virescent and yellow-center rosettes to pale green centers. 
When virescent plants are self ed, then green, virescent, and yellow are 
obtained, but no virescent plants have appeared in the progeny of 
yellow plants. 

It is hoped that in another place it will be possible to publish 
more extensive data and a complete discussion of the inheritance of 
chlorophyll deficient characters in Crepis which cannot be given at 
this time. 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 275 



GENERAL DISCUSSION 

In order to establish and preserve true breeding strains of the 
different types observed in the eultures, type plants were self- 
pollinated in successive generations. This most intense type of 
inbreeding affected these cultures in very much the same way as 
inbreeding has affected maize. Reduction in size and a slower rate 
of growth were the most noticeable results of inbreeding together 
with a slight increase in sterility. Most of the experiments to show 
the effect of inbreeding in plants have been with domesticated forms 
in which it is possible to have a genotypic constitution that might not 
exist in a wild state, because characteristics which would unfit the 
individual for survival in natural conditions are often preserved 
under the artificial conditions of cultivation. The inference is that 
wild species would differ in fewer genes than their cultivated relatives. 
However, the inbreeding experiments on Drosophila (Castle, 1906) 
produced no bad effects. Collins (1919) states that self-fertilization 
in teosinte, a wild relative of maize, causes no loss of vigor such 
as is known to occur in maize. On the other hand, Darwin (1876) 
concluded that wild species which are naturally cross-pollinated are, 
on the whole, adversely affected by inbreeding. It appears then that 
the results of inbreeding any race, cultivated or wild, would be an 
index to its genotypic heterozygosity or homozygosity. With this as 
a criterion, there is indicated a condition of germinal heterozygosity 
in Crepis capillaris. There appears to be a certain similarity between 
wild heterozygous species of Crepis and the cultivated races of maize 
in the type of recessive genes which persist in the genotype. In maize, 
a number of genes are present which produce characters that are so 
abnormal (sterility, extreme dwarfs, albinos) that they are propa- 
gated only with difficulty and would seldom be found under natural 
conditions. Examples of similar forms have appeared in inbred 
strains of Crepis. It may therefore be considered that natural selec- 
tion has not eliminated these genes from the germinal material of the 
wild species. The genes in Crepis which affect vigor also produce 
results comparable to similarly acting genes in maize. 

Evidence of the genotypic heterozygosity of capillaris has also 
been gained from another source. Seeds have been obtained from 
widely separated localities and grown side hy side in the greenhouse 



276 University of California Publications in Agricultural Sciences [Vol. 2 

and garden. The number of different forms resulting either in the 
first or later generations and as a result of controlled cross-pollinations 
show that the germinal material was indeed far from homozygous. 
It is of importance, because of some current theories regarding the 
influence of the habitat upon the genotype of a local species (Tures- 
son, 1922), to observe the behavior of these various forms when grown 
in as nearly identical conditions as can ordinarily be furnished in a 
greenhouse or garden. Plants belonging to many different genera 
were collected by Turesson from contrasted habitat localities in 
Sweden and grown together in a common garden. He found that 
in general each particular type of a species found in each of several 
different habitats maintained its characteristics in the absence of the 
habitat to which it seemed especially modified. He sees in such 
phenomena a refutation of the theory, now generally held, that the 
form predominating in a given locality occurred as a chance mutation 
or recombination and was preserved through natural selection. The 
theory substituted for this is Lamarckianism expressed in modern 
terminology, namely, habitat causes a change in the fundamental 
genotype of the species such that a phenotype is developed which 
permits the plant to nourish in a specialized habitat. His report 
deals principally with three types of plants in all his species, viz., 
dwarf forms, upright or erect forms, and spreading or procumbent 
forms, each of which was found in a location favorable to the existence 
of that type while unfavorable to the other types; and each thus 
becomes a demonstration of the effects of natural selection. In our 
study of Crepis forms we have not been fortunate enough to study 
wild populations of Crepis in all of the localities from which we have 
obtained seed, but we have produced hereditary strains of erect forms, 
spreading forms, and dwarf forms from the same habitat at Eureka, 
a fact which does not especially favor the existence of any one type. 
Dwarf forms have also appeared in cultures from other places (France 
and Denmark), whose definite habitat characteristics are unknown 
to us. Similar plant forms are well known to occur sporadically in 
many wild and domesticated species. Mutations giving rise to pros- 
trate and dwarf types in plants are not infrequent when compared 
to other types of change. If we accept the idea of a genoiypic response 
of the species to the habitat, are we not also admitting the inconstancy 
of the gene, a theory which is no longer tenable? Continuing the 
assumption, it is not clear why these different hereditary types, such 
as we have in Crepis, remain constant in a single unvarying habitat. 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 277 

The very fact that they do not approach a common type under culti- 
vated conditions supports the theory of the constancy of the gene and 
is evidence of the inability of the habitat to induce genotypic changes. 
The occurrence of duplicate genes in other plants has brought 
forth the opinion that they may indicate the presence of duplicated 
chromosomes. Three cases of duplicate genes have been found in 
Bursa (Shull, 1920), a plant having 32 chromosomes (4 X 8), while 
a case of triplicate genes is reported in a wheat (Nilsson-Ehle, 1909) 
which has 42 chromosomes. This number is three times the number 
(14) found in several species of Triticum (Sax, 1921). Several pairs 
of duplicate genes have been found in Crepis capillaris. No plants 
producing such ratios have been examined cytologically, but in no 
visible way do they differ from plants which give 3 to 1 ratios for 
the same characters. From what is known regarding the effect of 
duplication of single chromosomes or of whole sets of chromosomes 
in Datura (Blakeslee, 1922) and in Nicotiana (Clausen and Good- 
speed, 1924), it is difficult to suppose duplication of chromosomes has 
occurred here. That we have parallel mutations in identical loci 
of two chromosomes of the same kind derived from a form with a 
different number by some meiotic irregularity is equally improbable, 
for capillaris has but three pairs of chromosomes, no two similar 
enough in size to be construed as duplicates. There are several 
other ways to account for- the appearance of duplicate genes, some 
of which have been discussed by Shull (1918). Four of these possi- 
bilities are (a) the occurrence of similar gene mutations in different 
chromosome pairs; (6) the mating of non-homologous chromosomes; 
(c) duplication of entire chromosomes; and (d) duplication of 
sections of chromosomes. The possibility of a chromosomal dupli- 
cation as the cause of the origin of duplicate genes in Crepis is very 
unlikely, as has been shown above. The other possibilities cannot be 
dealt with so readily. It would appear, however, that, had duplica- 
tion of a section of a chromosome taken place, other characters, the 
genes for which were located in the duplicated section, should show 
similar inheritance ratios. As a matter of fact, two other characters 
in Crepis capillaris give ratios of 15 to 1, but in the one case tested 
(revolute X smooth ribs) the type of linkage demanded by such an 
hypothesis was not obtained. Mating of non-homologous chromosomes 
should also result in duplication of other genes which should show 
linkage relations. Although only a small amount of critical data is 
as yet available, no confirmation of the linkage relations demanded 



278 University of California Publications in Agricultural Sciences [Vol. 2 

by these two methods of gene duplication has been obtained. Shull 
rejected the idea of the occurrence of two independent mutations as 
a cause of duplication of genes in Bursa on the ground that the char- 
acters were of such a complex nature that the occurrence of two 
independent mutations producing identically the same somatic results 
was on the verge of impossibility. The characters in Crepis for which 
there are duplicate genes cannot be considered as complex, and the 
occurrence of similar mutations in non-homologous chromosomes 
therefore seems at the present time to be the more reasonable explana- 
tion of the origin of duplicate genes in this species. 

Sturtevant (1921) has shown that some points in the germinal 
material of a given species are more susceptible to mutations than 
others. There is evidence that such a mutating locus occurs in 
capillaris, for the same character, bald, has appeared in a number of 
strains derived from widely separated localities. The identity of 
these genes for bald has been proved in all cases except one (France) 
by crosses in which they proved to be allelomorphic. That a certain 
locus may mutate in the same way in other species is at least indicated 
by the fact that this character is now known to occur in four other 
species, none of which has been grown extensively among our cultures. 
The gene for bald is recessive in capillaris and is also recessive in the 
species cross, setosa X capillaris. 

No less interesting and unique is the group of complementary 
genes found in C. capillaris where the appearance of three such pairs 
of genes are concerned with the inheritance of leaf characters and a 
fourth with chlorophyll. It is not strange, however, that a greater 
number of complex gene relations should be encountered in a species 
containing a low number of chromosome pairs than in species having 
a larger number, unless the larger number results from reduplication. 
There is probably a minimum number of genes which is necessary 
in any species, and there is no reason to believe, a priori, that a species 
with a larger number of chromosomes need have a correspondingly 
larger number of genes. There is also evidence from Drosophila that 
the genes are distributed at random in each chromosome (except in 
cases of multiple allelomorphs) and among the chromosomes. When 
this basic number of genes is distributed among a large number of 
chromosomes, more characters will show simple types of inheritance. 
When this basic number is distributed in a fewer number of chromo- 
somes, there will necessarily result more complex types of inheritance. 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 



SUMMARY 

1. Plants of Crepis capillaris are largely cross-fertilized, and this 
mode of reproduction operates to maintain a condition of genotypic 
heterozygosity. 

2. Inbreeding wild plants thus produced results in the production 
of a number of pure races which show loss of vigor and reduction 
in size similar to the effects produced by inbreeding maize. 

3. Four sets of duplicate genes are found to be responsible for 
the inheritance of four different characters. Two of these characters 
are shown not to be linked. Duplicated genes do not indicate dupli- 
cated chromosomes, for each pair is morphologically different from 
the others. 

4. The recessive character 'bald' has appeared in a number of 
unrelated strains. This is evidence that a certain locus in one 
chromosome pair mutates more frequently in the same way than do 
other loci. The appearance of bald in other species may be due to 
a similar gene in each of these four species. 

5. Several types of chlorophyll variations have appeared. Some 
show monohybrid recessive relations when contrasted with the normal 
condition, while others show more complex relations. 

6. The different forms from widely separated localities show no 
tendency to approach a common type when grown continuously in 
the same place. 



It is with pleasure that the author acknowledges the helpful advice 
given by Professor Babcock and Professor Clausen throughout the 
progress of the work. 



280 University of California Publications in Agricultural Sciences [Vol. 2 



LITERATURE CITED 

Babccck, E. B., and Collins, J. L. 

1920. Interspecific hybrids in Crepis. I. Crepis capillaris (L.) Wallr. X C. 
, tectorum L. Univ. Calif. Publ. Agr. Sci., vol. 2, pp. 191-204. 

Blakeslee, A. F. 

1922. Variations in Datura due to changes in chromosome number. Am. Nat., 
vol. 61, pp. 16-31. 

Castle, W. E., Carpenter, F. W., et al. 

1906. The effects of inbreeding, cross-breeding, and selection upon the fer- 
tility and variability of Drosophila. Proc. Am. Acad. Arts and Sci., 
vol. 41, pp. 731-786. 

Clausen, E. E., and Goodspeed, T. H. 

1924. Inheritance in Nicotiana tahacum. IV. The trisomic character ' ' en- 
larged. " Genetics, vol. 9, pp. 181-197. 

Collins, G. N. 

1919. Intolerance in maize to self-fertilization. Jour. Wash. Acad. Sci., vol. 

9, pp. 309-312. 

Collins, J. L. 

1920. Inbreeding and cross-breeding in Crepis capillaris (L.) Wallr. Univ. 

Calif. Publ. Agr. Sci., vol. 2, pp. 205-216. 

1921. Eeversion in composites. Jour. Hered., vol. 12 ; pp. 129-133. 

1922. Culture of Crepis for genetic investigations. Jour. Hered., vol. 13, 

pp. 329-355. 

CORRENS, C. 

1912. Die neuen Vererbungsgesetze (Berlin), 75 pp. 

Darwin, C. 

1876. The effects of cross- and self-fertilization in the vegetable kingdom 
(London), 482 pp. 
Harris, J. A. 

1912. A simple test of the goodness of fit of Mendelian ratios. Am. Nat., 
vol. 46, pp. 741-745. 

Kristofferson, Karl B. 

1923. Monohybrid segregation in Malva species. Hereditas, vol. 4, pp. 44-54. 

Nilsson-Ehle, H. 

1909. Kreuzungsuntersuchungen an Hafer und Weizen. Lund's Univ. Ars- 
skrift, vol. 5, pp. 1-122. 

Basmuson, Hans. 

1916. Kreuzungsuntersuchungen bei Beben. Zeitschr. f. Indukt. Abstamm. 
Vererb., vol. 17, pp. 1-52. 

Rau, Venkata 

1923. Inheritance of some morphological characters in Crepis capillaris (L.) 
Wallr. Univ. Calif. Publ. Agr. Sci., vol. 2, pp. 217-242. 
Sax, Karl 

1921. Chromosome relationships in wheat. Science, n.s., vol. 54, pp. 413-415. 



1924] Collins: Inheritance in Crepis capillaris (L.) Wallr. 281 

Sears, Paul B. 

1922. Variation in cytology and gross morphology of Taraxacum. Bot. Gaz., 

vol. 73, pp. 425-446. 

Shoemaker, D. N. 

1919. A study of leaf characters in cotton hybrids. Am. Breed. Assoc, vol. 5, 

pp. 110-110. 
Shull, G. II. 

1914. Tiber die Vererbung der Blattfarbe bei Melandrium. Ber. Dent. Bot. 

Gesellschaft, vol. 31, pp. 41-80. 
1918. Duplication of leaf lobe factor in Bursa. Brooklyn Bot. Garden, Mem., 
vol. 1, pp. 427-443. 

1920. A third duplication of genetic factors in shepherds purse. Science, n.s., 

vol. 51, pp. 590. 

1921. Three new mutations in Oenothera LamarcMana. Jour. Hered., vol. 12, 

pp. 354-363. 

Stork, Harvey E. 

1920. Studies in the genus Taraxacum. Torr. Bot. Club Bull. 47, pp. 199-210. 

Sturtevant, A. H. 

1921. Genetic studies on Drosopliiln simulans III. Genetics, vol. 6, pp. 179- 

207. 
Tedin, Olcf 

1923. The inheritance of pinnatifid leaves in Camelina. Hereditas, vol. 4, 

pp. 59-64. 
Trow, A. H. 

1916. On "albinism" in Senecio vulgaris L. Jour. Gen., vol. 6, pp. 65-74. 

TURESSON, GOTE 

1922. The genotypical response of the plant species to the habitat. Hereditas, 

vol. 3, pp. 211-350. 



EXPLANATION OF PLATES 

PLATE 45 

Fig. 1. A rosette of the viridis race on the left with a pallid rosette on the 
right. 

Fig. 2. A typical rosette of the scalaris H6 race, showing blunt lobes, raffled 
Aving on midrib, constricted base of lateral lobes, and a twisting of the lateral 
lobes. 



[282] 



UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



COLLINSI PLATE 45 




Fig. 1 




Fig. 2 



PLATE 46 

Fig. 1. A rosette of simplex Z9 on the left, and at the right the aberrant 
pinnatifid type which appears in all cultures. 

Fig. 2. A rosette of the scalaris e29 race. 



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UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



[COLLINS] PLATE 46 




Fie. 1 




Fie. 2 



PLATE 47 

Fig. 1. A typical rosette of the pinnatifid leaf, scalaris e28. 
Fig. 2. A rosette showing revolute leaves. 



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UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



[COLLINSI PLATE 47 




Fig. 1 




Fig. 



PLATE 48 

Fig. 1. The bicephalic type of faseiation. 
Fig. 2. A mature dwarf II plant. 



[288] 



UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



ICOLLINS] PLATE 48 




% 







Fig. 1 



V 



IT 







Fig. 2 



PLATE 49 

Fig. 1. Two dwarf III plants with two normal sibs. 

Fig. 2. A typical plant from the race with the spreading habit. 



[290] 



UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



ICOLLINSI PLATE 49 




KB 

w 




Vr.i>. 



feS* 



ft&ft 



/% wfc* 




Fig. 1 




fc *A-A'\ 




Fig. 



PLATE 50 
Fig. 1. A typical plant of the erect growth habit. 



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UNIV. CALIF. PUBL. AGRI. SCI. VOL. 2 



(COLLINSI PLATE 50 




PLATE 51 

Fig. 1. Palea on the left with a receptacle of a normal plant on the right. 
Fig. 2. Three F, rosettes from the cross, scalaris X simplex. 



[294J 



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[COLLINSI PLATE 51 





Fig. 1 



I 




Fig. 



PLATE 52 

Fig. 1. Typical leaves from two plants of each of the parent strains and of 
the F 1} together with one leaf from each of eight F 2 plants, which show the results 
obtained when scalaris and simplex plants are crossed. Note the appearance in 
F 2 of the curved terminal lobe typical of the scalaris grandparent. 



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UNIV. CALIF, PUBL. AGRI. SCI. VOL. 2 (COLLINS, PLATE 52